Geometrical instruments – Gauge – With support for gauged article
Reexamination Certificate
2001-03-13
2003-08-12
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
With support for gauged article
C033S551000, C033S556000, C033S559000
Reexamination Certificate
active
06604295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microscopic geometry measuring device. More specifically, it relates to a microscopic geometry measuring device for accurately measuring a surface profile of LSI (large scale integration) and other semiconductor wafers.
2. Description of the Related Art
Conventionally, in accurately measuring the surface profile of a LSI and other semiconductor wafer, it is strongly desired to maintain a measuring force applied between a workpiece and a stylus in contact with the surface of the workpiece below a predetermined level. This is because damage to the workpiece and to the stylus can be prevented and the surface profile of the workpiece can be accurately reflected on the movement of the stylus by keeping the measuring force below a predetermined level. In order to meet the demand, a specially designed measuring device provided with a mechanism for controlling the measuring force below a predetermined level is used in accurately measuring the surface profile of semiconductor wafers.
The Applicant of the present application has proposed a measuring device disclosed in Japanese Patent Laid-Open Publication No. Hei 10-356187 as a conventional example of such measuring device. In
FIG. 6
, the measuring device
100
has a pivotable arm
101
, a stylus mechanism
103
having a stylus
102
provided on a lower surface of an end of the arm
101
to be in contact with a workpiece, a measuring force adjusting mechanism
104
for adjusting a measuring force applied to the stylus
102
, a displacement sensor
105
for detecting the position of the arm
101
, and a measuring force control circuit
106
for controlling the measuring force adjusting mechanism
104
. Here, reference numeral
101
A represents a pivot fulcrum of the arm
101
and
101
B represents a balance weight provided on the other end of the arm
101
. Displacements are recorded by computer
108
.
The Applicant has also proposed a stylus mechanism disclosed in Japanese Patent Application No. Hei 11-272451 as the stylus mechanism
103
used in the measuring device
100
.
The stylus mechanism
103
has a holder
103
A to be attached to the arm
101
, a stylus
102
held on the holder
103
A and having a contact portion
102
A to be in contact with the workpiece at the distal end thereof, a vibrator for resonantly vibrating the stylus
102
in an axial direction thereof, and a sensor for detecting a change in the resonance caused when the contact portion
102
A touches the workpiece.
The measuring force adjusting mechanism
104
is composed of a magnetic substance
104
A fixed on an upper side of the arm
101
and an electromagnetic actuator having an electromagnet
104
B disposed right above the magnetic substance
104
A. When the electromagnet
104
B is electrified, a repulsive or attractive force is caused between the magnetic substance
104
A and the electromagnet
104
B to move the arm
101
vertically, so that the stylus
102
provided on one end of the arm
101
vertically displaces. A distance between the surface of the workpiece and the one end of the arm
101
is controlled by controlling the electrical current to the electromagnet
104
B, thus keeping the measuring force applied between the stylus
102
and the workpiece below a predetermined level.
While the stylus
102
of the measuring device
100
is brought into contact with the surface of the workpiece, the stylus
102
is moved along the surface when measuring the workpiece. When the contact portion
102
A of the stylus
102
touches the surface of the workpiece, the output signal from the sensor changes in accordance with vibration change of the stylus
102
. The output signal is detected by a detecting circuit
107
. The measuring force control circuit
106
controls the measuring force adjusting mechanism
104
(electromagnetic actuator) based on information from the detecting circuit
107
, thus controlling the measuring force applied between the workpiece and the stylus
102
.
The measuring device
100
controls the movement of the arm
101
, i.e. the movement of the contact portion
102
A of the stylus
102
with a single electromagnetic actuator (the measuring force adjusting mechanism
104
). In order to move the contact portion
102
A to follow the workpiece surface while applying the predetermined level of measuring force, the contact portion
102
A has to be moved in a direction perpendicular to the workpiece surface in an order ranging from a nanometer to a millimeter.
However, there is 10
6
divergence between the nanometer and the millimeter order. When the movement of the contact portion
102
A is controlled with the above range by the single electromagnetic actuator, supposing the minimum value of the electromagnetic actuator is controlled at 1 mV (i.e., controlling 1*10
−6
mm at 1 mV), the maximum value has to be controlled at 1000 V (i.e. controlling 1 mm at 1000 V). Since the control value range is too wide, the measuring force control has been difficult.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a microscopic geometry measuring device capable of easily and accurately controlling the movement of the stylus from nanometer to millimeter order so that the stylus accurately follows the workpiece surface at a predetermined measuring force, thus reducing damage on the workpiece and the stylus and improving the measurement accuracy.
The inventors has contemplated combining two mechanisms, i.e. a fine feed mechanism for displacing the stylus within a range from a nanometer order to a micrometer order, and a coarse feed mechanism for displacing the stylus from a micrometer order to a millimeter order, to move the stylus within the range from the nanometer order to the millimeter order. For instance, a piezoelectric element (PZT) may be utilized as the fine feed mechanism, and an electromagnetic actuator may be utilized for the coarse feed mechanism, both of which can be constructed using a known technique. The combination of the known fine feed mechanism and the coarse feed mechanism may be conducted, for instance, by providing the stylus on a movable portion of the fine feed mechanism and providing a fixed portion of the fine feed mechanism to a movable portion of the coarse feed mechanism.
However, when the fine feed mechanism and the coarse feed mechanism are simply combined, the reaction force caused by the movement of the movable portion of the fine feed mechanism influences the fixed portion of the fine feed mechanism to apply force to the movable portion of the coarse feed mechanism provided with the fixed portion. In other words, a mechanical interference is caused between the fine feed mechanism and the coarse feed mechanism. When the mechanical interference is caused between the fine feed mechanism and the coarse feed mechanism, the stylus displaces in a complicated and uncontrollable manner, so that the measuring force cannot be controlled by an accurate control of the stylus movement. Uncontrollable measuring force applied to the stylus results in deterioration in measurement accuracy and, possibly, damage on the workpiece and the stylus.
In order to eliminate the mechanical interference between the fine feed mechanism and the coarse feed mechanism, the mass of the fixed portion of the fine feed mechanism may be set sufficiently greater than the mass of the movable portion, so that the reaction force of the movable portion is absorbed by the fixed portion to block the force applied from the fine feed mechanism to the coarse feed mechanism. However, in this case, since the mass of the entire fine feed mechanism is increased and the mass applied on the movable portion of the coarse feed mechanism for the fine feed mechanism to be provided is increased, the responsivity of the coarse feed mechanism is lowered, so that the measurement speed cannot be increased.
In order to eliminate mutual interference between the fine feed mechanism and the coarse feed mechanism without greatly increasing the mass of the movable portio
Hidaka Kazuhiko
Nishimura Kunitoshi
Okamoto Kiyokazu
Gutierrez Diego
Mitutoyo Corporation
Reis Travis
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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